Megillah 32A

משום דאפכי להו.

The Talmud answers: Because there are those who reversed the names in the baraita and attributed the position of R' Yehuda to R' Meir, and vice versa. Therefore, in order to avoid any lack of clarity, R' Zeira stated the halakha explicitly.

תנו רבנן: פותח ורואה, גולל ומברך, וחוזר ופותח וקורא. דברי רבי מאיר. רבי יהודה אומר: פותח ורואה ומברך וקורא.

A baraita states: When a person reads from the Torah, he should open the scroll and see the place from where he will read, furl it so that it is closed, and recite the blessing, and then he should again open the scroll, and read. This is the statement of R' Meir. R' Yehuda said: He should open the scroll, and see the place from where he will read, and, without closing it again, he should recite the blessing, and read.

מאי טעמא דרבי מאיר? כדעולא. דאמר עולא: מפני מה אמרו הקורא בתורה לא יסייע למתורגמן ⁠— כדי שלא יאמרו תרגום כתוב בתורה. הכא נמי: כדי שלא יאמרו ברכות כתובין בתורה.

The Talmud asks: What is the reason for R' Meir’s opinion that the blessing is not recited over an open scroll? The Talmud answers: His reasoning is in accordance with the statement of Ulla, as Ulla said: For what reason did the rabbis say that one who reads from the Torah should not assist the translator, but rather the translation should be exclusively said by the translator? In order that people should not say that the translation is written in the Torah. Here too, the scroll should be closed when reciting the blessings, in order that people should not say that the blessings are written in the Torah.

ורבי יהודה: תרגום ⁠— איכא למיטעי, ברכות ⁠— ליכא למיטעי.

And R' Yehuda is not concerned about this, as he claims that with regard to the translation, there is the possibility of people erring in this way, but with regard to the blessings, there is no concern about people erring. People will realize the blessings are not actually part of the Torah’s text because they are recited by each person who reads.